Chorionic Villus Sampling (CVS)

These are some reasons for having CVS:

• You got a "screen positive" result from enhanced First Trimester Screening (eFTS).
• You got a "high risk" result from Non-Invasive Prenatal Testing (NIPT).
• NIPT failed to give you a result after two tries or more.
• Your 11-14 week (nuchal translucency) ultrasound detected a possible problem with the baby. For example, some people choose to have a CVS if there is a large nuchal translucency, or there is a heart defect seen on ultrasound.
• There is a genetic condition running in your family, and you wish to have the baby tested for it before birth. 

If you are interested in CVS, speak to your health-care practitioner about referring you to a specialist in genetics. There, you will get more information about this publicly-funded test, and the team will arrange the CVS if it is an appropriate test for you. 

The procedure generally takes a few minutes. Some people have brief discomfort such as a cramping sensation. You can rest that day, and you will likely be able to go back to your regular activities within one to two days. 

Transcervical CVS. Illustration adapted from Genetic Counseling Aids, 7th Edition, Copyright 2020, permission for use granted by Greenwood Genetic Center.

There is a risk of miscarriage (losing the pregnancy) from CVS which can make it difficult to decide whether to have this procedure. It is important to remember that there is always the chance of pregnancy loss even if CVS is not done. CVS increases this risk by less than 1%. CVS does not cause other problems for the baby (such as birth defects). 

The type of results that you get depends on which centre did the CVS and the reason for testing. It is important to speak with your genetics specialist about what results you will get. All results are sent directly to your genetics specialist.

Rapid testing (also called QF-PCR)

You will likely get some results 3 to 4 days after the CVS. These results can tell you if the baby has one of the following chromosome differences: trisomy 21, trisomy 18 or trisomy 13 or a sex chromosome difference. 

Microarray testing

Depending on the hospital and the reason for testing, there might be a microarray test done from the same piece of tissue. Microarray testing can tell you whether there is material from other chromosomes that is extra or missing. These chromosome differences usually happen by chance in the sperm or the egg that made the baby. You get results from the microarray test in about 2 to 3 weeks.

• A short video created by Alberta Health Services explains the microarray test and possible results. In this video, the testing was done through a blood draw. The way the test works and type of results are the same when the microarray is done through CVS.

Other genetic testing 

Other genetic conditions can be tested in certain situations. Speak to your genetics specialist about whether there will be any other testing.